You're having another piece of cake? When was the last time you exercised? Those cigarettes are going to kill you. Did you clean the basement yet?

We all hate to nag, too.

Sit up straight. That's enough Doritos. Have you finished your homework? Are you sure? For once in your life, could you pick up your dirty socks? You're leaving the house looking like that?

We hate it. They hate it. So why do we do it? And, more important, how the hell can we stop? Oprah.com: How to save your relationship

The "whys" are the easiest to figure out. We do it because we care.

"Have you noticed that you nag people whom you love deeply?" asks Molly Barrow, Ph.D., a psychotherapist and the author of "Matchlines: A Revolutionary New Way of Looking at Relationships and Making the Right Choices in Love." It's somewhat warped, misguided love, she suggests, but it is love nonetheless.

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With the rest of the world, Barrow says, "you let them have their deadly consequences with hardly an 'I told you so.' But when you perceive the ones you love to be hurtling toward disaster, whether it's with trans fat, alcohol, drugs, or simply the failure to get a needed haircut, you just have to say something."

However, there's more than one problem with saying something, then saying it again and again and again and again. First, it doesn't feel like love. Not to my sons, who feel that I don't trust them to, say, get their schoolwork done their way. And not to their mother, who wonders why they just won't let her help them and why she can't learn to keep her meddling mouth shut.

When relationship expert and business consultant BJ Gallagher gets going on the subject, she makes naggers sound responsible for everything short of the terrorist threat.

"Nagging women," says Gallagher, author of "Women's Work Is Never Done... and Everything I Need to Know I Learned from Other Women," "are verbally castrating their husbands, emasculating them and turning them into resentful or resigned wusses. Women who nag their children are destroying what fragile self-esteem they might have, leaving their kids a legacy of years on a therapist's couch."

All that because I want my sons to double-check their homework? Please tell me that there are shades of gray here -- nagging that is necessary and nagging that is noxious. Oprah.com: What your kids really need the most

Barrow accepts that there is. She makes me feel better by categorizing what I do as "motherly loving" nagging, in which "the origin of the stream of 'Remember to...' sentences is a desire to nurture and be helpful."

There is also "be like me" nagging, she says. Couples who at first revel in their similarities but gradually come to see their differences often try to nag each other back to safe common ground, Barrow explains.

Parents also do this to children. From the inside it feels like love -- protecting kids from having to learn lessons the hard way, by telling them how you would do things. But from the outside it carries hints of something darker -- of trying to mold them into "what a child of mine should be." Children can be guilty of "be like me" nagging, too (ever heard a grown daughter nagging her mother to dress better?), for all the reasons that parents nag children and lovers nag each other.

And then there is what Barrow calls aggressive nagging: the "constant, no-let-up stream of criticism from a frustrated or angry mate who simply cannot be satisfied. This is nagging for self-benefit, not to help someone else. The nagger is in pain and wants you to be in pain, too." Oprah.com: Before your next fight, read this!

I have enough self-awareness to know I'm not guilty of aggressive nagging, but I am struck by the blurred boundary between Barrow's first two categories: the maternal instinct to guide, and the more problematic instinct to "change you into the person I want you to be." Yes, it is my job as a parent to make sure homework is done, and done responsibly. But my boys are 12 and 15, old enough to keep track of things on their own. Which means that my homework haranguing may be more about my own need to make them as successful in school as I was than it is about their knowledge of math or chemistry.

I am also struck by the realization that what I choose to nag about may have more to do with my irrational fears than with reality. I see my sons eating a bag of potato chips; I fast-forward to obesity and diabetes. They procrastinate over their homework; I see them on the unemployment line.

But what a waste if the effect of all my nudging is the opposite of what I intend -- if my message is heard not as "Look at all you can be" but rather "See what you are not?" What a shame if what I do in an attempt to strengthen my sons only weakens them -- and their relationship with me.

Which leads to the final, and most crucial, problem with nagging: It simply doesn't work. "You can't nag someone into permanent change," says Charles Goodstein, M.D., a psychoanalyst and clinical professor of psychiatry at NYU School of Medicine. Nagging appears to work, he says, because "it will produce a short-term result that looks positive. But in order for that result to recur, the nagging will have to recur."

In other words, the very fact that we feel we must nag is itself evidence that nagging doesn't work. If it did, we would say something once and never have to say it again.

The reason it doesn't work has to do with our psychological wiring, says Harris Stratyner, Ph.D, a psychologist and the director of addiction recovery services at the Mount Sinai Medical Center. It's likely that "when you nag someone, you're calling attention to something that already makes them feel bad," he says.

"By nagging, you make them feel like they are even more out of control. Say my wife can't stop herself from eating the whole package of cookies. The cause could be biochemical or emotional or hormonal or compulsive -- something beyond her control. By harassing her about her eating, I just make her feel worse, and that can perpetuate the problem."

But how to stop? I simply cannot accept that the alternative to nagging is doing nothing, going cold turkey, never saying anything at all for fear that you might say too much. Because while constant criticism is one dangerous end of a spectrum, isn't the opposite -- no criticism whatsoever -- an abdication of the responsibility that comes with love? Barrow was right, after all, when she said we nag the people we care about -- which is why if you ask me to give up nagging, it feels as if you're asking me to give up caring.

Stratyner offers a less all-or-nothing suggestion. He is a national advocate for a cognitive-behavioral technique called carefrontation, a play on words to distinguish the approach from the confrontations that most of us find ourselves embroiled in too often.

Referring again to his wife and her problem (purely theoretical, he assures me) with eating entire bags of cookies, he describes a more empathetic approach: "Instead of saying, 'You can't eat just one, can you? You have to eat the whole thing,' I could say, 'You know, I've noticed sometimes that when I buy a package of cookies, it's really hard for you not to eat all of them. I understand that. Would you like me to start buying something else to snack on? Because I love you and I care about your health.'" Oprah.com: The best way to get through to your partner

That sort of exchange, Stratyner says, "doesn't shame, doesn't blame." It approaches things from the point of view that "there is a problem" rather than "you are the problem."

It won't produce the desired result overnight, and it may not produce it ever; Stratyner is the first to point out that care-frontation is no magic bullet.

But it is, in his opinion, the option most likely to have a chance of effecting change because it puts you and the "naggee" on the same team, where you're in a position to combat the problem together. (Here it occurs to me that nagging because we love doesn't mean that without nagging there can be no love. Maybe giving up nagging only means giving up the delusion of control.)

Ironically, Stratyner's approach goes back to that thing my mother used to nag me about: "It's not what you say; it's how you say it."

Skeptically, I tried it recently. Instead of grilling the boys over their homework, which always feels like a me-against-them conversation, I changed my tone a bit: "I bet you have a lot of homework, huh?" I asked.

"Uh-huh."

"And I bet the last thing in the world you want is for me to bug you about it."

"Uh-huh."

"And I bet you're going to prove to me that I don't have to by going right upstairs and getting started."

"Uh-huh."

And it worked. True, it was barely disguised nagging. Which means it probably wasn't exactly what the good doctor had in mind. But wouldn't he be the first to concede how hard it is for people to change?